Method for the non-invasive sensing of physical matter on the detection surface of a capacitive sensor

• US 6,191,593 B1
• Filed: 12/17/1997
• Issued: 02/20/2001
• Est. Priority Date: 12/17/1997
• Status: Expired due to Term

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Tartagni, Marco, Gupta, Bhusan
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US08/992,002
• Time in Patent Office: 1,161 Days
• Field of Search: 324/662, 324/661, 324/687, 324/663
• US Class Current: 324/687
• CPC Class Codes: G01B 7/004 for measuring coordinates of points

Abstract

A capacitance sensor detects the absence/presence of physical matter on a sensing surface of the sensor. The capacitive sensor is a multi-cell sensor wherein each cell has one or more buried, protected, and physically inaccessible capacitor plates. The sensor is physically placed in an environment that is to be monitored for deposition of a particle, vapor, and/or drop of a foreign material on the sensing surface. All cells are initially placed in a startup condition or state. Thereafter, the cells are interrogated or readout, looking for a change in the equivalent feedback capacitance that results from an electrical field shape modification that is caused by the presence of physical matter on the sensing surface. When no such change is detected, the method is repeated for another cell. When a change is detected for a cell, a particle/vapor/drop output is provided. As an optional step, the sensor is provided with a layer of a material that is selectively reactive to or reactive with, a particle/vapor/drop of a known type of foreign material.

Claims

1. A method of detecting the presence of physical matter on a sensing surface of a sensor device, comprising the steps of:

providing a sensor device having an array of individual sensing cells arranged in a closely spaced physical configuration;

providing a dielectric layer covering said array, said dielectric layer providing said sensing surface;

providing a coating on said sensing surface that is responsive to physical matter;

detecting the presence of said known physical matter on said coating;

providing each sensing cell with an amplifier having an input and an output;

providing output-to-input feedback for each of said amplifiers, said feedback being sensitive to the presence of said physical matter on said coating;

providing said feedback for each of said amplifiers by way of a first capacitor plate that is placed under said sensing surface and that is connected to said input and, a second capacitor plate that is placed under said sensing surface in close spatial relation to said first capacitor plate and that is connected to said output; and

detecting the presence of physical matter on said coating.

2. The method of claim 1 including the step of:

burying said first capacitor plate and said second capacitor plate within said dielectric layer at a location that is closely spaced under said sensing surface.

3. The method of claim 1 including the step of:

placing said first and second capacitor plates on a common physical plane.

4. The method of claim 3 including the step of:

burying said first capacitor plate and said second capacitor plate within said dielectric layer at a location that is spaced from said sensing surface.

5. The method of claim 1 including the step of:

providing each of said amplifiers as signal-inverting amplifier; and

providing said output-to-input feedback for each of said amplifiers as negative-signal feedback.

6. The method of claim 5 including the step of:

placing said first and second capacitor plates on a common physical plane.

7. The method of claim 6 including the step of:

burying said first capacitor plate and said second capacitor plate within said dielectric layer at a location that is closely spaced from said sensing surface.

8. The method of claim 1 including the step of:

prior to enabling said device to detect the presence of physical matter on said sensing surface, momentarily shorting said input to said output for each of said amplifiers.

9. The method of claim 8 including the step of:

providing each of said amplifiers as signal-inverting amplifier; and

providing said output-to-input feedback for each of said amplifiers as negative feedback.

10. The method of claim 9 including the step of:

placing said first and second capacitor plates on a common physical plane.

12. The method of claim 1 including the step of:

providing each of said amplifiers as signal-inverting amplifier; and

providing said output-to-input feedback for each of said amplifiers as negative-signal feedback.

21. The method according to claim 1 wherein said coating is selectively responsive to the occurrence of vapor.

22. The method according to claim 21 wherein the vapor that the coating is selectively responsive to is an alcohol vapor.

23. The method according to claim 21 wherein the method said coating is responsive to is a water vapor.

24. The method according to claim 1 wherein said physical matter to which the coating is sensitive is an explosive type matter.

25. The method according to claim 1 wherein the matter the coating is sensitive to is a biological culture.

11. A method that operates to detect the presence of physical matter on a coating over a sensing surface, comprising the steps of:

providing at least one sensing cell;

providing a dielectric layer for said at least one sensing cell, said dielectric layer having said sensing surface located thereon;

providing a coating of a material that chemically reacts with a known physical matter on said sensing surface;

providing with an amplifier having an input and an output;

providing output-to-input feedback for said amplifier, said feedback being sensitive to the presence of physical matter on said coating;

providing said feedback by way of a first capacitor plate that is placed under said sensing surface and that is connected to said amplifier input, a second capacitor plate that is placed under said sensing surface in close spatial relation to said first capacitor plate and that is connected to said amplifier output; and

detecting when said known physical matter is present on said coating.

13. The method according to claim 11 wherein said physical matter to which the coating is sensitive is an explosive type matter.

14. The method of claim 11 including the step of:

burying said first capacitor plate and said second capacitor plate within said dielectric layer at a location that is spaced from said sensing surface.

15. The method of claim 11 including the step of:

placing said first and second capacitor plates on a common physical plane.

16. The method of claim 15 including the step of:

providing said amplifier as a signal-inverting amplifier; and

providing said output-to-input feedback as negative-signal feedback.

17. The method of claim 16 including the step of:

momentarily shorting said input to said output.

18. The method according to claim 11 wherein the matter the coating is sensitive to is a biological culture.

19. The method of claim 11 including the step of:

providing said amplifier as a signal-inverting amplifier; and

providing said output-to-input feedback as negative-signal feedback.

20. The method of claim 11 including the step of:

momentarily shorting said input to said output.

26. The method according to claim 11 wherein the coating is selectively responsive to the occurrence of vapor.

27. The method according to claim 11 wherein the vapor that the coating is selectively responsive to is an alcohol vapor.

28. The method according to claim 11 wherein the vapor that the coating is responsive to is a water vapor.